Advances in semi-conductor processing and logic design have permitted an increase in the amount of logic that may be present on integrated circuit devices. As a result, computer system configurations have evolved from a single or multiple integrated circuits in a system to multiple hardware threads, multiple cores, multiple devices, and/or complete systems on individual integrated circuits. Additionally, as the density of integrated circuits has grown, the power requirements for computing systems (from embedded systems to servers) have also escalated. Furthermore, software inefficiencies, and its requirements of hardware, have also caused an increase in computing device energy consumption. In fact, some studies indicate that computers consume approximately 13% of the entire electricity supply for the United States of America. As a result, there is a vital need for energy efficiency and conservation associated with integrated circuits. And as servers, desktop computers, notebooks, ultra-books, tablets, mobile phones, processors, embedded systems, etc. become even more prevalent (from inclusion in the typical computer, automobiles, and televisions to biotechnology), the effect of computing device sales stretches well outside the realm of energy consumption into a substantial, direct effect on The United States economy, as computing device related sales already have a large causal relationship with The United States Gross Domestic Product. Though specific statistics relevant to the United States of America have been presented here, the need for enhancing energy efficiencies and reducing energy or power consumption are applicable throughout the world.
For example, a computer system may comprise a processor, which may include multiple processing cores, an uncore area, a graphics processing unit, and many such processing blocks. One or more of these blocks may be operating on different and independent clock frequencies and may be, generally, referred to as “multi-frequency domains”. The domains (e.g., GPU, uncore) other than the processing cores domain (or core domain) may be referred to as non-core domain. The residency time of the cores in the power saving (or C) states (such as C0 to C7) may be determined by the power control unit or the operating system or the device drivers. However, the current techniques merely estimate the residency time of the non-core domains such as the GPU and such estimated residency times are mere estimates and may not be accurate or represent the actual residency times. As a result, a power state (or P-state) for the processor determined based on the estimated residency times of the non-core domains may not be optimal and power saving opportunities may be lost.